The present invention relates generally to magnetic flowmeters and, more particularly, to a magnetic flowmeter having electrodes in close proximity to its electromagnet.
Magnetic flowmeters have long been used to measure the flow of electrically conductive fluids. Magnetic flowmeters are governed by Faraday's law of electromagnetic induction, which provides that a conductor passing through a magnetic field induces of voltage across the conductor. Typically, a magnetic flowmeter exposes a conductive fluid to a magnetic field whose plane typically is oriented transverse to the direction of flow. As conductive fluid passes through the magnetic field, a voltage is induced. Such flowmeters typically include a pair of electrodes set apart from each other and in electrical contact with the fluid, to measure the induced voltage. Based on this measured voltage, the average velocity of the fluid can be determined.
Various configurations of flowmeters have been used, such as, bore-type and insertion-type. In a typical bore-type configuration, magnetic coils are mounted externally to a section of pipe and two electrodes extend into the interior of the pipe at opposite sides. The electrodes form an axis along the plane of the magnetic field, perpendicular to the fluid flow. Insertion-type flowmeters typically include a sensor assembly housing both a magnetic source and a pair of electrodes. In use, the sensor assembly is positioned with the electrodes in contact with the fluid flow.
For an accurate reading, it is beneficial to maintain a stable and strong magnetic field within the measured region between the electrodes. Notably, the strength of a magnetic field increases relative to its proximity to the magnetic source. Thus, it is beneficial to position the electrodes and the magnetic source in close proximity to each other. The magnetic source must also be sealed from the fluid, whereas the electrodes are in contact with the fluid. Thus, the electrodes and adjacent structure must provide adequate sealing against leakage.
Various approaches have been implemented for sealing the magnetic source from the fluid. These approaches commonly incorporate fairly complex structure, inhibiting proximity of the magnetic source to the electrodes. Moreover, current approaches can be relatively expensive to manufacture. Less expensive alternatives tend to sacrifice sensitivity and accuracy, which, in certain instances, can be attributed to imprecise positioning of the electrodes relative to one another or relative to the magnetic source.
It should, therefore, be appreciated that there remains a need for a magnetic flowmeter that is cost effective to manufacture while providing precise positioning of the electrodes relative to one another and in close proximity to the magnetic source. It should also be appreciated that there remains a need for a magnetic flowmeter incorporating an effective seal about the electrodes. The present invention fulfills this need and others.